The present invention relates to a method for limiting the rate of rotation of the break-up rollers of an open-end spinning unit of the type in which the break-up roller is mounted without a mechanically-connected drive and is caused to rotate without contact by the spinning rotor which is arranged coaxially thereto. The invention also relates to apparatus operating according to the method.
In such an arrangement, the break-up roller can be driven, without mechanical contact with the drive source, by a stream of air produced by the spinning rotor or by eddy current fields produced with the aid of a system of magnets which create a reciprocal magnetic effect between the break-up roller and the spinning rotor.
Such a so-called indirect drive has the advantage of involving a particularly simple structure; the break-up roller is carried along, without any additional drive means, by the stream of air or the magnetic effect, in the direction of rotation of the spinning rotor, which is connected to a drive assembly.
One drawback of the indirect drive, where no mechanical connection exists between the driving and the driven component, is that the rate of rotation of the break-up roller is dependent inter alia, on the type and quantity of the fed-in fibers. Thus, when the machine is empty there exists the danger that the break-up roller will rotate at too high a rate.
Such unduly high rates of rotation could be avoided by providing the break-up roller with centrifugally or speed controlled friction surfaces, for example braking jaws or braking pins, which become effective when a limit speed is being exceeded, to brake the break-up roller. Such control devices, however, are subject to wear and are structurally complicated so that they do not represent a satisfactory solution in the normal case.